I. Field of the Invention
The invention is directed to a process for electroplating of metal utilizing an electrode containing multiple coating layers. The electrode may find use in an electroplating system containing organic substituents in which the consumption of the organic substituent is significantly decreased or in systems where it is desirable to suppress the oxidation of a species in an electrochemical cell.
II. Description of the Related Art
In traditional plating systems, anodes are utilized which are fabricated from the same metal being plated. Known as “soluble” anodes in the industry, the anodes supply both the electrical current and replenish the electrolyte with the metal ions being plated.
In order to improve the current plating technology, by increasing current density and modifying cell design, the use of insoluble anodes has been substituted for the traditional soluble anode. These insoluble anodes, also known as dimensionally stable anodes, such as coated titanium anodes, however, significantly increase the consumption of the organic constituents added to the electrolyte. Such disadvantages affect the plating characteristics and cost effectiveness of the plating process.
In U.S. Pat. No. 6,251,254, there is taught an electrode adapted for chromium plating from trivalent chromium baths. The electrode comprises a conductive base, an electrode material layer of iridium oxide thereon, and a porous oxide layer of silicon, molybdenum, titanium, tantalum, zirconium or tungsten formed on the surface of the electrode material layer.
U.S. Pat. No. 4,310,391 to Okinaka, et al, teaches an electrode structure useful as a counter electrode in gold plating which exhibits long life and reduced undesirable side reactions in the gold plating process, including reduction in the consumption of buffer material and formation of trivalent gold. The electrode surface consists of a coating mixture of oxides of certain group eight elements and oxides of certain valve metals.
It would be desirable, however, to provide an anode for an electroplating system containing organic constituents, which does not significantly decrease the amount of organic constituent lost via oxidation in the system. It would also be desirable to provide an anode for electrochemical processes where there is a need to minimize the oxidation of an oxidizable species in solutions. For example, inhibiting the oxidation of chloride in systems with low levels of chloride to minimize the production of chlorine and/or hypochlorite, which may be undesirable byproducts.